The Backstreet Boys are back, and so are Ricky Martin and Boyz II Men — they’re among the roster of ’90s-fame musicians who now have big residencies in Sin City. With millennials driving the resurgence of 1990s nostalgia in fashion and TV, it’s no surprise the Las Vegas Strip has been hit with the ’90s revival.

Celine Dion and Britney Spears have held court in Vegas ballrooms with successful long-running shows, and stiletto-loving Mariah Carey concluded her Caesars Palace residency in July.

For the Backstreet Boys, the glitz and glamour of the city merits a stylish production that’s “Larger Than Life” — the name of their ubiquitous 1999 hit and current Planet Hollywood residency, which launched as a three-month stint in fall 2016 but has been extended through February of next year.

“As the show continues to go on, eventually we will want to add and update the costumes to keep the show fresh and fun,” said the group’s costume stylist, Tierney Burchett, whose Peripheral Apparel luxury sportswear line launches an e-commerce website in September. “Each piece was custom-made head-to- toe for each of them, and it gives them a strong stage presence.”

Currently, the bandmates — Nick Carter, Howie Dorough, Brian Littrell, A.J. McLean and Kevin Richardson — open each show in all-white leather suits with metallic silver boots by Saint Laurent. “Kevin actually wears them in metallic red for the third act as well,” Burchett said.

Some of the other footwear brands used onstage include Hugo Boss, Magnanni, Alexander McQueen and Christian Louboutin.

“A.J. and Brian are huge sneaker guys, so they love to bring in shoes from their personal closets to mix it up a bit,” she said, adding: “Their favorite brands are John Varvatos and Nike.”

In total, the band has four wardrobe changes throughout the show, and while styles play to their personalities, the looks reflect their development as polished men of today — not the boys of yesteryear.

“It’s Vegas, so we definitely wanted to step outside of our comfort zone,” Burchett said. “The guys have never worn anything with sequins before, so that was a big change, but the main focus with costumes for this show was to be either ahead of our time or as present as possible.”

In Vegas, the days of visiting just to win a jackpot are long gone. Shopping, dining and over-the-top shows are now the main attraction. Last year, a survey conducted by the Las Vegas Convention and Visitors Authority found that 52 percent of visitors said the main purpose of their trip was pleasure, and only 4 percent named gambling.

For Grammy-winning girl group TLC, who stopped in Vegas last month for their “I Love the ’90s” tour, their nostalgic fans not only want to hear their favorite hits but want to see iconic outfits from past music videos.

“The one thing I use for inspiration is to try to create something people want to re-create for Halloween — that’s how you know it’s good,” said the group’s costume designer, Brea Stinson, who reimagined TLC’s futuristic wardrobe in 1999’s “No Scrubs.”

“They are Michael Jackson fanatics, so I tried to bring in Michael Jackson’s ‘Bad’ era mixed with the [all-black] look from ‘No Scrubs’ — it’s a hybrid but recognizable to TLC’s aesthetic; sexy but a little bit of a tomboy.”

Tionne “T-Boz” Watkins and Rozonda “Chilli” Thomas (third member Lisa “Left Eye” Lopes died in 2002) played to an audience at the open-air Downtown Las Vegas Events Center, which Stinson said presented challenges because alterations had to be made to adjust for the sweltering heat. In fact, one week ahead of the Vegas show, Thomas suffered dehydration while performing in Concord, Calif., at an amphitheater, Stinson recalled.

“This year’s costumes are made of vegan leather and satin, with lots of hardware,” Stinson said, adding that changes such as swapping leather for all-satin jackets and short-sleeve versions of the costumes in lighter fabrics were made. “We create sex appeal and a cool factor; they still dance like it’s 1992.”

Watkins and Thomas wear only one costume throughout the tour — mixing the look with Isabel Marant hiking boot sneakers in black with a natural gum sole and New Rock combat boots in black with silver accents.

“We have to make sure [the shoes] have grips because they dance so much, and you never know the condition of stages,” Stinson said. “Another important factor is ankle support, so sneakers will be a high-top and boots will be a midcalf silhouette for ankle support.”

Some other strategic measures the costume designers took with footwear include lacing and fit. “If Tionne is wearing a high-top or boot, then we tie it around her ankle instead of lacing it — we take it and go around the ankle for added support and double-knot it in the back to make sure it doesn’t come undone. I double-knot Chili’s laces twice in the front.”

Burchett said she customized the Backstreet Boys’ footwear with rubber soles for shoe styles that are “too slippery,” but for the full head-to-toe costume changes, she incorporated timesaving tricks of the trade. “We exchange laces out for elastic and add zippers to the shoes to avoid laces in general, and we always double-knot everything,” she added.

“Boots and sneakers are the easiest for the guys to dance in, so that’s pretty much all we have them wearing onstage besides the Act Two dress shoe, which they made sure they could dance in them before we made any final decisions,” said Burchett. “The crazier the choreography, the safer the shoe.”